From 2f86b07cfa2535c2e527f4a0d6b6577a9a5f1cc7 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 26 Nov 2016 13:40:10 +0800
Subject: [PATCH] Added a parser for Oric-format MFM disks. Causing my first
 disk to load!

---
 Storage/Disk/Formats/OricMFMDSK.cpp | 61 +++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 11 deletions(-)

diff --git a/Storage/Disk/Formats/OricMFMDSK.cpp b/Storage/Disk/Formats/OricMFMDSK.cpp
index c522e092f..59b4b2b10 100644
--- a/Storage/Disk/Formats/OricMFMDSK.cpp
+++ b/Storage/Disk/Formats/OricMFMDSK.cpp
@@ -8,6 +8,7 @@
 
 #include "OricMFMDSK.hpp"
 #include "../PCMTrack.hpp"
+#include "../Encodings/MFM.hpp"
 
 using namespace Storage::Disk;
 
@@ -37,26 +38,64 @@ unsigned int OricMFMDSK::get_head_count()
 
 std::shared_ptr<Track> OricMFMDSK::get_track_at_position(unsigned int head, unsigned int position)
 {
-	long offset = 0;
+	long seek_offset = 0;
 	switch(geometry_type_)
 	{
 		case 1:
-			offset = (head * track_count_) + position;
+			seek_offset = (head * track_count_) + position;
 		break;
 		case 2:
-			offset = (position * track_count_ * head_count_) + head;
+			seek_offset = (position * track_count_ * head_count_) + head;
 		break;
 	}
-	fseek(file_, (offset * 6400) + 256, SEEK_SET);
-
-	// TODO: upon review, the file format actually seems to omit clock bits. So it's not an MFM capture.
-	// A consumer must contextually guess when an FB, FC, etc is meant to be a control mark. So turfing
-	// the data over directly as below isn't correct.
+	fseek(file_, (seek_offset * 6400) + 256, SEEK_SET);
 
 	PCMSegment segment;
-	segment.number_of_bits = 6250*8;
-	segment.data.resize(6250);
-	fread(segment.data.data(), 1, 6250, file_);
+
+	// The file format omits clock bits. So it's not a genuine MFM capture.
+	// A consumer must contextually guess when an FB, FC, etc is meant to be a control mark.
+	size_t track_offset = 0;
+	uint8_t last_header[6];
+	std::unique_ptr<Encodings::MFM::Encoder> encoder = Encodings::MFM::GetMFMEncoder(segment.data);
+	while(track_offset < 6250)
+	{
+		uint8_t next_byte = (uint8_t)fgetc(file_);
+		track_offset++;
+
+		switch(next_byte)
+		{
+			default:
+				encoder->add_byte(next_byte);
+			break;
+
+			case 0xfe:	// an ID synchronisation
+			{
+				encoder->add_ID_address_mark();
+
+				for(int byte = 0; byte < 6; byte++)
+				{
+					last_header[byte] = (uint8_t)fgetc(file_);
+					encoder->add_byte(last_header[byte]);
+					track_offset++;
+					if(track_offset == 6250) break;
+				}
+			}
+			break;
+
+			case 0xfb:	// a data synchronisation
+				encoder->add_data_address_mark();
+
+				for(int byte = 0; byte < (128 << last_header[3]) + 2; byte++)
+				{
+					encoder->add_byte((uint8_t)fgetc(file_));
+					track_offset++;
+					if(track_offset == 6250) break;
+				}
+			break;
+		}
+	}
+
+	segment.number_of_bits = (unsigned int)(segment.data.size() * 8);
 
 	std::shared_ptr<PCMTrack> track(new PCMTrack(segment));
 	return track;